Rendering objects only for left or right camera in 2.8
Managed to solve the problem by creating three collections. 
In left scene is collection "left", and the collection "right" is instanced here but not rendered.
in right scene is  collection "right", and the collection "left" is instanced here but not rendered.
And finally collection called "both" is linked to both scenes.

For linking or instancing a collection from another scene you have to go to "Scenes" view in Outliner, this enables to see collections from other scenes. You can then right click on the collection you want to link or instance here.